The St. Mary's County commissioners agreed to move forward with the new Patuxent River Naval Air Museum and Visitor's Center despite some concerns that no estimate of the project's operating costs had been reviewed.

The Board of Commissioners approved a memorandum of understanding last week between the county and the State Highway Administration that described the scope of the project and the estimated costs and said the county would accept $3.4 million in federal funds that was appropriated by Congress in 2003.

The agreement estimated that the project, a renovation of the museum, could cost $7.4 million, including $3.4 million in federal funds, $975,000 in additional county funds, $975,000 in state bonds and $1.5 million in private funds raised by the museum association. The county has already contributed more than $1 million.

But commissioners President Thomas F. McKay (R-At Large) said he is concerned that the museum association had not submitted estimated operating costs despite a written request to do so.

"When you make any kind of decisions to expand or build something new, that's one of the basic items you need in place," McKay said. "You could find the easy part is raising $8 million to build it, and the tough part could be finding the funding to keep it going."

Because the building will have a glass facade and potentially high heating and cooling costs, McKay estimated that it could take $800,000 to $1 million per year to operate. But retired Rear Adm. Gus Eggert, the president of the Patuxent River Naval Air Museum Association, told the commissioners that he doesn't "sense the urgency right now" to provide those figures and doesn't want to give an inaccurate estimate. He said the county may need to commit more money to operate the museum.

"That's what [the commissioners] are worried about, and I don't blame them. But you have to be realistic," he said. "We already have the most popular attraction in Southern Maryland, and it's going to grow fantastically."

The museum opened in 1978. Eggert said it is one of 12 official Navy museums in the country, features a display of about 20 aircraft and attracts about 65,000 visitors a year. The fundraising for the expansion began several years ago and at one point was scheduled to open last year. The museum association has reached its $1.5 million goal but has yet to find a funding source for an additional $600,000 needed for a mezzanine, stairs and elevator, among other things, said Gary Hodge, a consultant on the project.

On June 15, the county received approval from the state Board of Public Works to demolish a vacated building on the property, Hodge said. The demolition, and other site preparation, should begin next month, Eggert said.

"That will be a milestone," he said. "This will be a dramatic change; people will see something physically happening."

Then the plan is to put out bids for construction in November, begin building in March and finish in 18 months to two years, Eggert and Hodge said. But McKay suggested that the time line could be delayed further without the operating estimate.

"With the county not having that, it could delay or have an impact on whether there's sufficient funds in the county's budget to allow that project to go forward," McKay said.